CHAPTER XV
DR. GILES STARTLES HIS HEARERS
TILL Dr. Giles hesitated; but when Flora laid a caressing hand on his shoulder, and looked up at him with imploring eyes, the last vestiges of his opposition vanished.
"Well, William," said he, "since you are determined upon going, I don't see but that I shall be obliged to let you make the trip. If there were any real danger, I could not, of course, think of such a thing; but, as a matter of fact, you ran more risks in coming here on the ship than you will in going through the earth. This voyage, being something out of the ordinary run, naturally frightens people more than a greater danger with which they are familiar. Novelty breeds fear, just as familiarity breeds contempt."
Flora beamed with delight as the doctor thus practically gave his consent, while William returned profuse thanks. Visions immediately floated through his mind of a speedy and successful trip, and he pictured his arrival in New York, where, of course, he would be received in triumph, and fêted like a hero. He would not have been a mortal boy had he not been dazzled by the glory that seemed in store for him.
Had he realized then the dangers and difficulties to be passed, he might well have paused and turned back. But, with youthful optimism, he saw none of these, and he faced the ordeal with a brave and cheerful heart.
Our hero was brought back from his reflections by the doctor's next remark:
"We now come to the question of money, William. I hardly suppose you will wish to take the hundred pounds with you on your trip?"
"No, sir," said William; "I should like mother to get them as soon as possible."
"Very well; then I'll despatch a messenger at once with the money, and will myself add a second hundred pounds to the amount. But where can we find your mother?"
"I left her in the park early this morning, sir, while I went out to look for work; and I told her I should be back by noon, if possible, or, if I 
"'WELL, WILLIAM,' SAID HE, 'SINCE YOU ARE DETERMINED UPON GOING, I DON'T SEE BUT THAT I SHALL BE OBLIGED TO LET YOU MAKE THE TRIP.'"
"Not at all," replied Dr. Giles. "But now that I come to think of it, my boy, you have not yet asked any questions about the trip you are going to undertake, but seem willing to go into it blindfolded."
"I thought all I should have to do would be to get into the car," said William. "I supposed you would press the button and do all the rest."
"Even so, I should think you'd want to know something of the dangers that you will have to run."
"I'd much rather not," replied William. "What's the use of knowing about a danger when you can't help yourself? While I am falling through the earth I'll be as helpless as a baby; so what's the good of frightening me by telling me of the danger! You would only make me nervous and want to back out."
"I guess there's not much danger of your backing out," said Dr. Giles, after a careful survey of the manly face before him. "Besides, you will not be so wholly helpless as you seem to think."
At this juncture Mr. Curtis, who had entered the room, thought it necessary to put in an oar.
"I think, with the doctor, William, that you won't be absolutely helpless while you're falling. I remember, when I was a youngster like you, I used to go swimming with a number of other boys. There was a very high dock from which we used to dive, and one day a comrade, in a spirit of mischief, pushed me overboard when I was n't looking. I was badly frightened, I can tell you, when I felt myself falling; but I knew that if I fell flat I should be badly hurt, so I kicked and squirmed as I went down, and succeeded in turning myself around, so that I reached the water head first, and was n't hurt a bit."
"Yes," said William, " the same thing has often happened to me. Besides, I know that cats, when they fall, always manage to land on their feet. Some years ago, my mother one day heard her pet canary fluttering about in its cage, and knowing that something was wrong, she rushed to the window, and spied a large black cat, that had climbed up the wistaria-vine and was trying to get at the cage.
"Mother was so angry and excited that she caught the cat by the back of the neck and threw it out into the middle of the street. She was, of course, sorry the moment she had done it, for this was the fifth-story window, and there was a stone pavement below. She looked out in agony, expecting to see the poor beast crushed to death by his fall; but—would you believe it!—that cat coolly turned around in the air, fell right side up on his four paws, and disappeared like a streak of lightning, without being hurt in the least!
"Now, that cat was a great deal worse off than I shall be, because he had nothing to hold on to, while I can cling to the car. I suppose that Dr. Giles has got a mattress fastened to the floor, and by holding on to this I shall be all right."
Dr. Giles had been listening to this entire dialogue with an amused face, but he now thought it time to interfere.
"I think that neither of you has the faintest idea of the conditions that will prevail during the trip," he observed pleasantly. "If you imagine that your fall through the earth is going to be like the fall of a cat through the air, you are very much mistaken, and it will therefore perhaps be well for me to give you some idea of what will really take place. To begin with, I want to ask you a few questions, William, on a point that Mr. Curtis and I have been discussing. I understand that you studied physics at school?"
"Only the very elements," answered William, hastily, fearing that his imperfect knowledge was about to be put to the test.
"Well, that ought to be sufficient, for all the problems you will meet with in your trip are elementary ones. But tell me first what you know about the force of attraction at the center of the earth."
"Why, there is no attraction of gravitation at the center of the earth—or rather, the attraction is the same on all sides, so it is neutralized. A body placed at the very center of the earth would weigh absolutely nothing; if I were there at this moment I should weigh nothing at all, not even one tenth of an ounce."
"Your answer is perfectly correct so far, William, and we all agree with you. Now tell us, please, what you think your weight will be during your trip in the car."
"Why, at the beginning I shall weigh just as much as I do now, that is to say, one hundred pounds. But as I go down my weight will be less, because, instead of being attracted downward by the entire mass of the earth, that part which I have passed, being above me, will attract me upward. Thus my weight will become lighter and lighter until, when the car reaches the center of the earth, I shall weigh absolutely nothing; then, as the car progresses, and I pass the center and go up toward New York, my weight will gradually return again; and when I finally do reach New York I shall weigh one hundred pounds, as before."
"That 's just exactly what I said!" exclaimed Mr. Curtis, glancing at our hero approvingly.
"I think so, too," observed Flora, timidly. "Well," said Dr. Giles, "your reasons are good, and would be true of bodies at rest; but it will not be true of William in the car. A body at rest at the center of the earth would weigh absolutely nothing; a body at rest half-way to the center would only have about half its normal weight; while a body near the surface would have its complete normal weight. But in William's case it will be altogether different."
"How so?"
"Why, unless I am very much mistaken, at the very moment his car starts he will at once lose all his weight and float up in the air like a feather!"